how many MPG's do I get?

I accidentaly blew a fuse while installing a new radio in my 1991 camry. After I changed the fuse the gas gauge wouldn't go lower than about 1/2 tank. I ran out of gas once not knowing this. After I filled it up again it returned to full and seems to work just fine. I put on about 150 miles since I last refueled and the gas gauge has returned to 1/2. I don't know if this is right because I don't know exactly how many MPG's I get. The car is 2.0L with 5 speed manual. Do you think I should refuel it again or should I wait and see if the gauge is right? I think it should get about 350-400 miles to the tank with no problem.
 
Thanks
 
ps-it has fuel capacity of 16 gallons

Easiest just to keep it full man you dont want to keep running out that isn't good for the fuel pump or injectors etc.